Operating method for a mine-sweeping system, and mine-sweeping system for detonating sea mines

ABSTRACT

A method for operating a mine-sweeping system and corresponding mine-sweeping system, wherein the mine-sweeping system includes at least one drone for detonating sea mines. The drone has at least one magnet element for magnetically detonating the sea mines. The method includes a) translationally moving the at least one drone in the water and b) carrying out a first rotational movement of the drone with respect to a first degree of rotational freedom.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2020/067826 filed 25 Jun. 2020, and claims the benefitthereof. The International Application claims the benefit of GermanApplication No. DE 10 2019 212 105.5 filed 13 Aug. 2019. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a method for operating a mine-sweepingsystem, wherein the mine-sweeping system comprises at least one dronefor detonating sea mines. In this case, the drone comprises at leastmagnet element for magnetically detonating the sea mines. The inventionfurthermore relates to a corresponding mine-sweeping system.

BACKGROUND OF INVENTION

Known systems for remotely clearing sea mines use unmanned drones whichare equipped with magnetic coils or with permanent magnets fordetonating magnetic mines. These magnet elements generate strongmagnetic fields, which can cause the sea mines to detonate. In thiscase, the drones are configured in such a way that, at the distancetypical for detonation, they are not damaged by the detonation.

Such drones may have a drive system of their own, for example the GermanNavy has remotely controllable boats of the “Seehund” [seal] type, whichare equipped with a diesel engine. The magnet element here is designedas a magnetic coil and, for detonating the mines, is integrated in thehull of the remotely controllable boats. The magnetic coil itself is inthis case typically formed by a multiplicity of turns of copper cable.

In addition to such drones that float on the surface, there are alsoknown underwater mine-sweeping drones, which may either also have adrive of their own or be towed along by other (under)water vessels.

The self-driven drones may be driven, for example, by an electric motor.In general, in the case of such self-driven drones, the magnet elementsmay basically be designed either as additional magnet elements or elsethey can carry out a dual function, in which, in addition to theirfunction for detonating mines, they also serve for generating a magneticexcitation field in the electric motor. Examples of such mine-sweepingsystems with a magnetic dual function are described in DE102016203341A1and in the German application that has not yet been disclosed and hasthe application number 10 2018 217 211.0.

Many of the known mine-sweeping systems, rather than having just onedrone, have a plurality of interconnected drones, wherein each of saiddrones comprises one or more magnetic elements for detonating the seamines. Such an assembly of linked drones which are jointly towed as achain by a transport ship is described, for example, in EP0475834B1.This interlinking of a plurality of drones serves to reproduce aspecified magnetic signature of a hypothetical ship as accurately inevery detail as possible. This is necessary because the relativelycomplex sea mines nowadays are configured to respond only to certainmagnetic signatures which correspond to the signatures of certain typesof ships. The sea mines therefore cannot readily be detonated by randommagnetic signals. On the contrary, a certain time profile of a magneticmagnitude, for example the magnetic flux density measured by the seamine, is necessary in order to cause a detonation. This time profile hasto correspond as substantially as possible to the predefined magneticsignature of a certain type of ship, said signature being anticipated bythe sea mine, in order to be able to bring about the detonation of thesea mine.

In order to be able to reproduce the magnetic signature of a predefinedtype of ship as accurately as possible, use is generally made, accordingto the prior art, of mine-sweeping systems, the longitudinal extent ofwhich lies within the range of the length of the type of ship “to besimulated”. For this reason, the chain length of a plurality of linkeddrones of a mine-sweeping system is frequently of the order of magnitudeof 100 m or more. The number of interlinked drones can be, for example,in the range between 3 and 7, with it being possible, with a highernumber of drones, to typically achieve better accuracy in thereproduction of a certain defined magnetic signature.

A disadvantage of the mine-sweeping systems from the prior art is thatthere is a comparatively high outlay on apparatus because of the highnumber of drones used and because of the length of the chains of dronesthat are used.

SUMMARY OF INVENTION

It is therefore an object of the invention to specify a method foroperating a mine-sweeping system that overcomes the aforementioneddisadvantage. In particular, the intention is to provide an operatingmethod which, in comparison to the prior art, permits as accurate areproduction of a predefined magnetic profile as possible with a reducednumber of drones and with a reduced chain length. It is a further objectto specify a corresponding mine-sweeping system.

These objects are achieved by the method and the mine-sweeping system asdescribed.

The method according to the invention serves for operating amine-sweeping system, wherein the mine-sweeping system comprises atleast one drone for detonating sea mines. In this case, the dronecomprises at least one magnet element for magnetically detonating thesea mines. The method comprises the following steps: a) translationallymoving the at least one drone in the water, and b) carrying out a firstrotational movement of the drone with respect to a first degree ofrotational freedom.

The at least one drone can basically either be self-driven here, or itcan be towed by another water vessel. In each case, the drone is thesame element of the mine-sweeping system that, by means of at least onemagnet element, can lead to a magnetically induced detonation of the seamines. The at least one magnet element is therefore intended to beconfigured in such a way that the generated magnetic flux densitysuffices for detonating a sea mine in the environment of the drone.

The drone can in principle either float on the water surface or can bemoved in a diving manner under the water surface. Basically, acombination of these “floating” and “diving” modes is also possible. Ineach case, according to step a), a translational moving of the drone isintended to take place. Said translational moving can be in particular amovement parallel to the water surface. The floating embodiment caninvolve in particular a movement along the water surface. The divingembodiment can involve a corresponding movement along a lower levellying parallel to the water surface. In other words, it canadvantageously involve a horizontal translational movement. However, itis also possible and, under some circumstances, advantageous for thetranslational movement to additionally also contain a vertical componentsuch that, during the horizontal movement, a diving depth of the droneis simultaneously varied. In this case, during the translationalmovement, the drone can therefore also sink or rise in the water. Inconjunction with the present invention, it is essential only that thetranslational movement in step a) has at least a horizontal component,i.e., in other words, a directional component parallel to the watersurface.

In step b), in addition to said translational moving, a rotationalmovement of the drone in the water is carried out. The sequence of saidtwo steps a) and b) is basically as desired here: for example, they canbe carried out either simultaneously or else successively, in particularin multiple successive changes. The drone, as a body which is freelymovable in water, basically has three independent degrees of rotationalfreedom. The rotation of the drone is intended to be a rotationalmovement with respect to at least a first of said three degrees ofrotational freedom. The effect generally advantageously achieved by therotational movement is that, for example, the magnetic flux density isadditionally varied at a target location which lies in the environmentof the drone.

The described “target location” can be in particular a location in theenvironment of the mine-sweeping system, at which a sea mine can bebrought to detonate. This target location does not have to be limited toa point-like region, but may in particular also involve a spatiallyextended detonating range which can have in particular the shape of aconical target region. The effect which can advantageously be achievedby the described interaction of the translational moving and therotational movement of the drone is that a predefined magnetic profilewhich substantially corresponds to the magnetic signature of a giventype of ship can be formed at the target location. Particularlyadvantageously, said target location lies upstream of the drone withrespect to the translational moving (i.e. “as seen in the direction oftravel”). The effect can thus be achieved that the magnetic signaturerequired for detonating the sea mines is simulated at the targetlocation before the drone (or else the mine-sweeping system as a whole)reaches the target location. In this way, a greater distance can bemaintained between the mine-sweeping system and the detonating seamines. The risk of damage to the mine-sweeping system upon detonation ofthe sea mines is thereby reduced.

In other words, by means of the described combination of translationalmoving and targeted rotational movement, a desired magnetic profile canbe projected ahead onto a target location located upstream of the dronein the direction of travel. It is particularly advantageous if, in thiscase, for example, the magnitude of the magnetic flux density at saidtarget location lying ahead is higher than in the remaining regions inthe environment of the drone. The effect which can be achieved bycarrying out the rotational movement (optionally in combination with theadditional control variables described further below) is that, at thetarget location, not only is a certain magnetic flux density generatedat a certain time, but that, at the target location, a certain profileof the flux density over time is also generated, which substantiallycorresponds to the magnetic signature to be reproduced. The magneticprofile reproduced in this way can be in particular a predefined profileof the magnitude of the magnetic flux density over time, one or moredirectional components of the magnetic flux density, or else acombination of said aforementioned variables.

The effect which can advantageously be achieved by this described“projection ahead” of a predetermined magnetic profile is that themine-sweeping system brings about a reliable detonation of sea mines,with it being possible at the same time, in comparison to the prior art,to reduce the number of required drones and/or the length of the chainof drones that is used. This reduction in outlay on apparatus can beachieved in that, by means of the rotational movement of the drone, anadditional degree of freedom is available in order to reproduce acomplex magnetic profile at a given target destination. The extent ofthe mine-sweeping system can thus be reduced in particular by the factthat the movement of an extended drone chain past the sea mine is atleast partially replaced by “projecting ahead” the desired magneticsignature to the potential location of the sea mine. This affords thefurther advantage that, under some circumstances, the detonation canalso take place at a greater and therefore safer distance from themine-sweeping system.

The mine-sweeping system according to the invention has at least onedrone for detonating sea mines. The drone comprises at least one magnetelement for magnetically detonating the sea mines. In addition, thedrone comprises at least one control element for bringing about a firstrotational movement of the drone with respect to a first degree ofrotational freedom. In particular, said control element is configured tobring about the rotational movement while the drone floats on a watersurface or dives below the water surface. It is therefore intended to bea control element for bringing about a rotational movement of the dronein the water. It can basically either be an active or a passive controlelement. An active control element is intended to be understood here asmeaning a control element which has a dedicated drive element in orderto actively bring about the corresponding rotational movement. A passivecontrol element is intended to be understood here as meaning a controlelement which does not have a drive of its own, but rather can interactwith a further drive (for example the translational drive of the droneor an external towing drive by means of a mother ship or a guidingdrone) in order to bring about a rotational movement of the drone withthe aid of the water flow. With the mine-sweeping system according tothe invention, the advantages described further above in conjunctionwith the operating method can be realized.

Advantageous refinements and developments of the invention emerge fromthe claims and from the following description. The described refinementsof the method and of the mine-sweeping system can advantageously becombined with one another.

In a generally particularly advantageous manner, the drone has alongitudinal axis A, and the first degree of rotational freedomcorresponds to a rotational movement about said longitudinal axis. Inother words, the rotational movement may involve rolling or heeling ofthe drone. The elongated shape of the drone is particularly in order topermit a low-resistant movement in the water. The rotational movementabout the longitudinal axis is correspondingly the rotational movementwhich is possible with the smallest possible resistance in the water.This applies in particular for a generally advantageous, substantiallyrotationally symmetrical configuration of the drone with thelongitudinal axis A as axis of symmetry.

However, as an alternative to the above-described rotation about thelongitudinal axis, it is also possible and advantageous under somecircumstances if the first degree of rotational freedom corresponds to arotational movement about an axis which lies perpendicular to thelongitudinal axis. For example, such an axis of rotation can lieperpendicular to the longitudinal axis and (when the drone is orientedhorizontally in the water) substantially parallel to the water surface.In other words, the rotational movement can then involve pitching ortrimming of the drone. According to a further alternative, the axis ofrotation can lie perpendicular to the longitudinal axis and (when thedrone is oriented horizontally in the water) substantially perpendicularto the water surface. In other words, the rotational movement can thenbe a yawing or classic rotation. In principle, however, rotations arealso conceivable and under certain circumstances advantageous, in whichsaid described classic maritime degrees of rotational freedom arecombined with one another such that a rotation with respect to an axisof rotation lying obliquely in relation to the longitudinal axis of thedrone is carried out.

With each of the described rotational movements, a magnetic flux densitybrought about at the target location can advantageously be variedparticularly readily if the at least one magnet element is configuredfor forming a magnetic field in which at least one pole axis forms anangle α, which is different from zero, with the axis of rotationrelevant to the first degree of rotational freedom. Said axis ofrotation can particularly advantageously be the longitudinal axis of thedrone. A pole axis is intended to be understood here as meaning ingeneral an axis of symmetry of the magnetic field, on which two magneticpoles are arranged (a north pole and a south pole). Such a pole axis isalso referred to among experts as a magnetic axis. The angle α canadvantageously be in the range between 10° and 90° and particularlyadvantageously can be in the range between 45° and 90°. A rotation aboutthe respective axis of rotation then brings about a particularlysignificant change in the magnetic field generated in the environment bythe drone. This significant change can be in particular a change of amagnitude, generated at the target destination, of the magnetic fluxdensity or else also a change in the value and/or the sign of one ormore individual directional components of the flux density.

In a generally advantageous manner, the method can comprise thefollowing additional step: c) carrying out a rotational movement of thedrone with respect to an additional second degree of rotational freedom.

Such a combination of at least two degrees of rotational freedomtherefore corresponds to a more complex rotational movement by means ofwhich a specific magnetic profile can be reproduced even more preciselyat a predefined target location. The two degrees of rotational freedomto be combined with each other can be generally selected as desired fromthe three classic maritime degrees of rotational freedom describedfurther above (i.e. in each case two of the degrees of freedom ofrolling/heeling and/or pitching/trimming and/or yawing/rotating). In aparticularly advantageous manner, all three of the aforementioneddegrees of rotational freedom can also be combined with one another inorder to permit an even more precise reproduction of a given magneticprofile at a given target location. In general, in a manner similar tostep b) which has already been described, this additional step c) can becarried out simultaneously or else in an alternating manner with thetranslation in step a). Steps b) and c) may in principle also be carriedout either simultaneously with each other or successively.

According to a further advantageous embodiment, the method can comprisethe following additional step: d) changing a diving depth (T) of thedrone.

The diving depth is intended to be understood here as meaning in generalthe vertical distance of the deepest point of the drone from the watersurface. In the case of a drone which floats and is not completelyimmersed in the water, said diving depth can also be smaller than thevertical height of the drone. This can therefore then in particularinvolve an immersion depth of a drone floating on the surface.

It is also possible, by means of such a variation in the immersiondepth/diving depth, for the time profile, which is generated at a giventarget location, of the magnetic flux density to be adapted even moreprecisely to a specific magnetic profile. In order to generate aspecified profile of the magnetic flux density over time, the at leastone degree of rotational freedom can therefore advantageously becombined with a variation in the diving depth. In general, similarly tostep c) that has already been described, this additional step d) can becarried out simultaneously or else in an alternating manner with thetranslation in step a). Steps b), c) and/or d) can in principle becarried out either simultaneously with one another or at least partiallysequentially.

Alternatively or in addition to the described variation in the divingdepth, it is also possible (either within step d) or in a furtheroptional step) for the speed and/or the direction of the horizontalmovement or of the horizontal movement component of the drone to bechanged. This can also advantageously permit an even more precisereproduction of a specified magnetic profile at a certain location.

According to a first advantageous embodiment, the at least one magneticelement of the drone can be a permanent magnet. Such a permanentlymagnetic drone has a comparatively low outlay on apparatus, andtherefore it can be produced easily and is simple to operate. It is alsocomparatively robust.

According to an alternative second advantageous embodiment, the at leastone magnet element of the drone can be an electrical coil element. Anadvantage of such an electrically magnetized drone is that a desiredmagnitude of the magnetic flux density can be modulated relativelyeasily in particular by means of an adjustable current flow. Theelectrical coil element can be, for example, either a normallyconducting or else also a superconducting coil element. When asuperconducting coil element is used, with the latter having acomparatively small overall size, particularly high magnetic fluxdensities can be generated.

It may also be advantageous to combine the first embodiment with atleast one permanent magnet and the second embodiment with at least oneelectrical coil element with each other such that a plurality ofdifferent magnet elements are present next to one another. In generaland independently of the precise design of the magnet element or of themagnet elements, the latter can be configured for forming a magneticfield, the pole number of which is advantageously between 2 and 16.

In an embodiment having at least an electrical coil element, the methodcan generally advantageously comprise the following additional step: e)varying an operating current of the electrical coil element over time.

By this means, the magnetic flux density at a specified target locationcan be additionally influenced in a particularly simple manner. Incombination with the variation possibilities already described furtherabove, a specified magnetic profile can thus be reproduced even moreprecisely. In general, similarly to steps b), c) and d) that havealready been described, this additional step e) can be carried outsimultaneously or else in an alternating manner with the translation instep a). Steps b), c), d) and/or e), if present, can also in principlebe carried out either simultaneously with one another and/or at leastpartially sequentially.

In a generally particularly advantageous manner, the at least one dronecan be a self-driven drone. A general advantage of a self-driven droneconsists in not requiring an additional separate mother ship which wouldbe at risk in the event of a detonation of a sea mine. The risks for themother ship and the crew thereof are thus advantageously avoided.

For example, the drone can have an electric drive. For this purpose, thedrone can comprise an electric motor which can drive, for example, apropeller of the drone. The at least one magnetic element serving fordetonating mines can advantageously simultaneously be a magnet elementof an excitation device of the electric motor, similarly as is describedin DE102016203341A1 and in the German application which has not beenpublished and has the application number 10 2018 217 211.0. In thiscase, it is generally particularly advantageous if the electric motorhas a correspondingly weak magnetic shielding.

As already mentioned, the sequence of the described steps may beconfigured differently. Thus, according to a first advantageous variant,both steps a) and b) can take place simultaneously. This is intended tobe understood as meaning that the two steps mentioned at least partiallyoverlap in time. They therefore do not absolutely have to have preciselythe same duration. For example, it is thus possible and, under somecircumstances, advantageous if step a) lasts for a longer period of timet_(a) and step b) is carried out within the period of time t_(a) in oneor more individual and comparatively shorter time intervals t_(b). Theindividual time intervals t_(b) may in principle be configured hereeither to be of the same length as one another or else to differ inlength. It is only essential, in the case of this first embodimentvariant, for step b) to take place while step a) lasts, i.e. while thedrone is moved. Step b) is advantageously carried out several times insuccession during said movement. In this way, a controlled simulation ofthe desired magnetic signature can take place during the movement of thedrone and therefore during its change in position. An advantage of thisfirst embodiment variant is that the time for moving the drone cansimultaneously also be used for the specific variation of the magneticfield generated in the environment. A specified, extended spatial areacan therefore be covered by the mine-sweeping system in a comparativelyshort overall period and can nevertheless be particularly reliably freedfrom active sea mines.

According to an alternative second variant, both steps a) and b) may,however, also take place successively. In particular, both steps caneach be carried multiple times in a repeated changing sequence. In otherwords, the drone can in each case alternately be moved translationallyfor a distance in order then, at the reached position, to bring about aspecific reproduction of the predefined magnetic profile by means of theat least one rotational movement. These two steps a) and b) can eachalternately be carried out successively for a multiplicity of times inorder thereby to reliably scan a spatially extended area and to free thesame from sea mines. An advantage of this second embodiment variant canconsist in being able to particularly accurately reproduce a specifiedmagnetic profile at a given fixed target location by decoupling thehorizontal movement and specific modulation of the magnetic fieldgenerated in the environment.

In general and irrespective of the precise sequence of the two describedsteps a) and b), it is advantageous in every case if step b) is carriedout a plurality of times successively, wherein, during the individualimplementations of step b), the drone takes up in each case a differentposition with a projection onto the water surface. Step b) can berepeated in particular in a periodically recurring sequence. In thiscase, the duration of the individual time intervals t_(b) for step b)can in each case advantageously be in a range of between 1 second and 3minutes, particularly advantageously between 10 seconds and 3 minutes.Such a time interval is sufficient in order, at a given position of thedrone, to reproduce a specified magnetic signature at at least onetarget location and in particular also at a plurality of targetlocations in the environment of this position.

The mine-sweeping system can advantageously also comprise a plurality ofdrones for detonating sea mines. It can therefore also be providedwithin the scope of this invention that a plurality of such drones arelinked in the manner of a chain and move together through the sea.However, by means of the advantages of the invention that are describedfurther above, the number of individual drones and/or the spatial extentof the chain can be reduced in comparison to the prior art, with aspecified magnetic profile nevertheless being able to be reproducedsufficiently accurately.

In such an embodiment with a plurality of drones, it is particularlyadvantageous if all of said individual drones have the featuresdescribed further above. All of the individual drones can expediently ineach case have at least one magnet element for magnetically detonatingsea mines. The translational moving according to step a) isadvantageously coupled for the individual drones of the chain. However,a certain translational relative movement of the individual drones isnot ruled out here since a particularly accurate reproduction of a givenmagnetic profile can therefore also be achieved therewith. Therotational movement according to step b) has to be realized at least forone of the drones in the chain. However, it is particularly advantageousif all the drones of the chain carry out such a rotational movementaccording to step b). This rotational movement can basically take placeeither in a manner synchronized for all of the drones of the chain orelse independently of one another. If different rotational movements ofthe individual drones are carried out separately, a particularlyaccurate reproduction of a given complex magnetic profile can in turn beachieved.

In such an embodiment with a chain of a plurality of linked drones, itis particularly advantageous if at least one of the drones isself-driven. This one drone can then tow the remaining drones of thechain behind it. Alternatively, it is, however, also possible and, undersome circumstances, advantageous if all of the drones of the chain havea drive of their own. A translational relative movement and a separaterotation of the individual drones is therefore made possibleparticularly easily.

According to an advantageous embodiment of the mine-sweeping system, theat least one drone can be a self-driven drone. Irrespective of whethersaid drone is self-driven or whether it is moved passively, the controlelement for bringing about the first rotational movement can basicallybe either an active or a passive control element. It is particularlyadvantageous if the at least one drone has a drive element of its ownwhich can drive both the translational movement of the drone and therotational movement of the drone. In order to trigger the rotationalmovement, in this case there can optionally be an additional passivecontrol element, for example a rudder or a flap. However, an additionalactive control element for the rotational movement can also be present,for example a separate motor.

In a generally advantageous manner and independently of thetranslational drive of the drone, the at least one control element canbe, for example, a rudder, a flap or a motor. The motor can particularlyadvantageously be a separate motor which is provided in addition to atranslational drive motor of the drone. In particular, this can be aseparate electric motor. It can be arranged, for example, axially in thevicinity of the center of gravity of the drone where it can particularlyeffectively trigger a rolling movement.

In general and independently of the drive of the drone and the preciserealization of the control element, the drone can be designed in such amanner that a magnetic flux density of at least 5 mT, in particular atleast 50 mT or even at least 500 mT can be achieved in a region outsidethe drone (but in the vicinity of its housing). With such high magneticflux densities in the vicinity of the drone, a magnetic mine at arelatively far target location can be detonated even from a relativelygreat distance. For this purpose, an outer wall of the drone can beformed from an amagnetic material. In conjunction with the presentinvention, an amagnetic material is intended to be understood as meaningin general a material having a relative permeability μ_(r) of at least300.

In addition, the at least one drone can generally advantageously alsocomprise a further detonation system for acoustic and/or electricaldetonation of sea mines. According to a particularly advantageousembodiment of the mine-sweeping system, the latter can in turn comprisea plurality of drones for detonating sea mines.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below using a number of exemplary embodimentswith reference to the attached drawings, in which:

FIG. 1 shows a schematic illustration of a magnetic signature, to bereproduced, of a ship,

FIG. 2 shows a schematic sectional illustration of a mine-sweepingsystem according to a first exemplary embodiment of the invention,

FIG. 3 shows a rectangular coil,

FIG. 4 shows a three-dimensional profile for a magnetic flux densityformed with the rectangular coil of FIG. 3,

FIG. 5 shows the dependency of the magnetic flux density on the distancefrom the coil center for various directions in space,

FIG. 6 shows the dependency of various components of the magnetic fluxdensity on the revolution angle for a magnetic quadrupole, and

FIG. 7 shows a schematic illustration of a mine-sweeping systemaccording to a second example of the invention.

DETAILED DESCRIPTION OF INVENTION

In the figures, identical or functionally identical elements areprovided with the same reference signs.

FIG. 1 shows a schematic illustration of a magnetic signature 1 of aship which has a longitudinal extent in the region of approximately 200m. This magnetic signature is intended to be reproduced as accurately inevery detail as possible by a mine-sweeping system in order therefore,for a modern complex sea mine, to simulate the passing by of acorresponding ship and thus to bring the sea mine to detonate. FIG. 1illustrates the dependency of the magnitude of the magnetic flux densityB on the position of an observation point, for example below the ship.Accordingly, the horizontal distance d of the observation point from thecenter of gravity of the ship is illustrated in meters on the abscissa.This therefore involves a position-dependent magnetic signature 1. Byway of example, only the magnitude of the magnetic flux density isillustrated in FIG. 1. Corresponding additional curves arise analogouslyif, depending on the horizontal distance, the individual directioncomponents (for example in the Cartesian directions in space x, y and z)of the magnetic flux density are taken into consideration. Moderncomplex sea mines are frequently configured to compare a measuredprofile of the magnitude of the magnetic flux density and also of theindividual direction components thereof with the known magneticsignatures of predefined types of ship and to detonate only if there isa sufficiently high correspondence.

In the following, a magnetic signature is understood as meaning ingeneral the dependency of the magnetic flux density on a positioncoordinate as is illustrated in FIG. 1. Since, however, a sea mine isnot spatially extended, it can measure the detected magnetic parameternot as a function of the location, but only as a function of the time.This time dependency is calculated from the positional dependency, shownin FIG. 1, of a magnetic parameter in combination with the speed of thepassing ship and the (shortest) distance at which the ship passes thestationary sea mine. The sea mine therefore actually measures atime-dependent magnetic profile which is produced as a function of themagnetic signature outlined in FIG. 1. The task of a mine-sweepingsystem is therefore to simulate the corresponding time-dependentmagnetic profile of such a passing ship as well as possible,specifically ideally not only for the magnitude of the magnetic fluxdensity B that is illustrated in FIG. 1, but simultaneously also for oneor more direction components. Complex characteristic patterns forcertain defined types of ship can be produced in this case.

FIG. 2 shows a schematic partially perspective sectional illustration ofa mine-sweeping system 21 according to a first example of the invention.In the example shown, this mine-sweeping system 21 comprises only asingle drone 22 which here is diving in the water 20 and below the watersurface 29, specifically with a diving depth T. Alternatively oradditionally, however, a use floating on the water surface also comesinto consideration. The drone 21 has a central longitudinal axis A andmoves along a travel direction v which coincides here with thelongitudinal axis A.

The drone 22 is a self-driven drone which can itself be moved in thewater by means of an electric motor 23 and a propeller 24 mechanicallycoupled thereto, and does not have to be towed by a mother ship.Alternatively, however, an embodiment with only a passive towing driveis also conceivable. The drone 22 is configured to generate, at a targetlocation 26, a time-dependent magnetic profile which corresponds asexactly as possible to the magnetic profile which a ship traveling pastat a typical travel speed and having a specified magnetic signaturewould generate. In other words, the intention is to simulate themagnetic signature of a known type of ship in order to bring a sea minepositioned at the target location 26 to detonation.

In order to generate the desired time-dependent magnetic profile at thetarget location 26, the drone 22 is equipped with at least one magnetelement. Only by way of example are a plurality of different magnetelements shown for the drone 22 in FIG. 2: this drone thus has firstly aplurality of coil elements 27 a which are used as excitation coils ofthe electric motor 23. However, these coil elements 27 a carry out adual function and serve at the same time to contribute to the generationof the desired magnetic profile at the target location 26. In addition,in the rear part of the drone 22, further coil elements 27 b are shownwhich likewise contribute to the generation of the desired magneticprofile, but are not part of the electric motor. Of the two types ofcoil 27 a and 27 b, there can be in each case one or more in such adrone. It is particularly advantageous if the individual coil elementscan be fed with a variable current such that the amplitude of thegenerated magnetic field can be additionally modulated. In the frontregion, the drone 22 additionally has a permanent magnet 28 which isillustrated here by way of example as an annular disk magnet. Inprinciple, however, such permanent magnets can be present in the dronein any form and also in any number. Such permanent magnets can alsocontribute to the generation of the desired magnetic profile. However,the arrangement of the individual different types of magnet elements 27a, 27 b and 28 within a drone should be understood here as merely beingby way of example. Although a plurality of such elements may be arrangedwithin a drone, it is, however, generally sufficient if a dronecomprises at least one magnetic element in order to bring about amagnetic detonation of a sea mine.

In the example of FIG. 2, the current direction of travel v of the droneis coaxial with the longitudinal axis A. In principle, however, thetranslational movement of the drone may also have different directioncomponents. In FIG. 2, the direction of travel v is slightly oblique inthe coordinate system shown (with the Cartesian direction coordinates x,y and z). The direction of travel v does indeed have a relatively largehorizontal direction component within the xy plane which lies parallelto the water surface. However, it additionally also has a slightcomponent in the z direction which corresponds here to a slight sinkingof the drone.

In addition to this translational movement, the drone, however, alsoexecutes at least one rotation movement with respect to at least onedegree of rotational freedom. The three independent degrees ofrotational freedom of the drone are denoted by the arrows r1, r2 and r3in FIG. 2. In this case, the degree of rotational freedom r1 correspondsto rolling or heeling of the drone, the degree of rotational freedom r2corresponds to pitching or trimming, and the degree of rotationalfreedom r3 corresponds to yawing or rotating. A complex rotationalmovement may also take place in which the drone is rotated about aplurality of the aforementioned degrees of rotational freedom. In eachcase, the described rotation of the drone modulates the magnetic fluxdensity generated at a certain time at the target location 26. Thisrelates in general both to the magnitude and to the individual directioncomponents of the flux density. The rotational movement can therefore beused in order, at the target location 26, to reproduce thetime-dependent magnetic profile, which is intended to correspond to themagnetic signature of a passing ship, as accurately as possible. Inorder to improve the reproduction of the desired magnetic profile evenfurther, the described rotational movement can optionally be combinedwith a variation of the diving depth T and/or with a variation of theoperating current of the coil element 27 a or 28 a and/or with avariation of direction of travel v and/or travel speed.

It is generally particularly effective if, during the travel of thedrone 22 through the water, at least the described rotation movement iscarried out multiple times successively. It can therefore be achievedthat a desired magnetic profile is reproduced successively at differenttarget locations 26. This is true irrespective of whether the rotationalmovement, which is carried out, is carried out in each casesimultaneously with the translational forward movement or in analternating manner with the translational forward movement of the drone.

It is particularly advantageous if the rotational movement of the droneis at least a rotational movement with respect to the first degree ofrotational freedom r1, in other words if it comprises rolling or heelingof the drone. In order to permit such rolling, the drone 22 of FIG. 2 isprovided with a control element 25. This can be either an active controlelement (for example an electric motor) or else a passive controlelement (for example a rudder or a flap). Corresponding further controlelements, not illustrated specifically here, can also be provided forthe rotational movement with respect to the other degrees of rotationalfreedom r2 and/or r3.

The mine detonation by the described mine-sweeping system 21 isparticularly effective if, at the target location 26, a comparativelyhigh magnetic flux density in comparison to the other environment of thedrone is generated, wherein said target location 26 can still lieupstream of the drone, as seen in the direction of travel v.Particularly advantageously, it can lie upstream of the drone, as shownin the direction of travel in FIG. 2, and below the drone with respectto the water surface. The desired magnetic profile can in each case beprojected ahead to said target location and sea mines arranged at thetarget location can already be brought to detonation at a certaindistance from the drone passing by, which reduces the risk of damage tothe drone during detonation.

It is intended to be clarified with the following FIGS. 3 to 6 how thedescribed rotational movement of the drone contributes to varying themagnetic field generated at a target location 26 by means of the atleast one magnet element. FIG. 3 thus shows an approximatelysquare-shaped rectangular coil 31 as can be used, for example, as coilelement 27 a or 27 b in the drone of FIG. 2. The Cartesian coordinatedirections x, y and z shown in FIG. 3 illustrate only a local coordinatesystem here and are not necessarily intended to correspond to thespatial directions illustrated in FIG. 2. However, the local coordinatesystem is retained in the following FIGS. 4 and 5. When current flowsthrough the rectangular coil 31, a two-pole magnetic field is generated,the pole axis of which is denoted here by P.

FIG. 4 shows the simulated three-dimensional profile of the magneticflux density B formed by the rectangular coil 31 of FIG. 3 when aconstant current flow is provided. The profiles are shown for themagnitude of the magnetic flux density, the profiles being produced fromthe center point Z outward for three different surface sections: asquare-shaped cutout of the xy plane, a square-shaped cutout of the xzplane and a square-shaped cutout of the yz plane each having an edgelength which corresponds to a multiple of the coil diameter. For thispurpose, the corresponding surface cutouts are divided by hatching intoregions of similar magnetic flux density, with the division into thevalue ranges having been selected in accordance with a logarithmicscale. The end points of the value ranges are indicated in arbitraryunits, with the numerical values only being intended to clarify that alogarithmic scale has been used. It can readily be seen in FIG. 4 that,for a certain distance from the center, the magnitude of the magneticflux density B which is formed depends greatly on the spatialorientation of the observation point. By means of a rotational movementof the drone which carries the coil, a significant modulation of themagnetic flux density generated at an outer target location cantherefore be achieved. This modulation is particularly powerful if therotational movement takes place about an axis of rotation which enclosesan angle different from 0 with the pole axis P. In other words, thefield distribution in the environment changes particularly powerfullyif, during the rotation, the magnetic pole axis P itself is tilted.

FIG. 5 shows the dependency of the magnetic flux density B, formed bythe rectangular coil 31 of FIG. 3, on the distance d from the coilcenter M. This dependency is shown for different directions in space:the curve Bx thus shows the distance dependency for various positionsalong the x axis. The curve By analogously shows the distance dependencyfor various positions along the y axis. Finally, the curve Bw shows thedistance dependency along the diagonal direction (within the xz plane)which is denoted by w in FIG. 4. The values for the magnitude of themagnetic flux density B are in turn each specified in arbitrary units ona logarithmic scale. The values for the distance d are specified inmultiples of the coil diameter. The conspicuous points of the two curvesBy and Bw mark the locations of the conductors through which currentpasses. It is shown that, at relatively great distances of a pluralityof coil diameters, the magnitudes of the flux densities on the x axisare significantly larger than on the other two axes. It is also shownthat, by means of a corresponding rotation of the drone, the magneticflux density generated at the target location can be powerfullymodulated. The direction components (not shown here) can also becorrespondingly modulated, with it also being possible to bring about asign change in the event of a correspondingly high angle of rotation.

The embodiments in conjunction with FIGS. 3 to 5 apply not only to thecoil geometry under consideration here but in a similar manner also forother coil shapes. The powerful direction dependency of the generatedmagnetic flux density applies in a similar manner also to permanentlymagnetic dipoles. Even in the case of multi-pole magnet systems, arotation of the excitation device can bring about a significantmodulation of the magnetic flux density generated. This is intended tobe clarified by way of example by FIG. 6 for a magnetic quadrupolearrangement: FIG. 6 thus shows the dependency of various components ofthe magnetic flux density on the revolution angle 63 for a magneticquadrupole which can be realized, for example, by a symmetricalarrangement of four electrical coil elements. The upper part of FIG. 6shows how the magnitude of the magnetic flux density 61 (here inarbitrary units) varies over a half revolution of 180° about thequadrupole arrangement. This revolution has been simulated with aconstant radius. The magnetic flux density 61 here in each case reachesa maximum in the region of the two magnetic pole axes P1 and P2 while itdecreases by a significant factor in the regions in between.

It is shown in the lower part of FIG. 6 how the direction components 62of the magnetic flux density vary during a corresponding revolution. Thevalues for the direction components 62 are also specified here inarbitrary units. The curve Br denotes the profile of the local radialdirection component, while the curve Bt shows the profile of the localtangential direction component. As seen over the half revolution of180°, powerful modulations each having two zero crossings are producedfor the two curves. Therefore, via corresponding rotation of a dronewith a magnetic quadrupole, a powerful modulation can be achieved bothfor the magnitude of the magnetic flux density and for the individualdirection components. In particular, a specified complex profile of theindividual direction components can be reproduced.

If, therefore, the sea mine which is to be detonated carries out acomparison with a stored desired profile not only for the magnitude ofthe magnetic flux density, but also for the individual directioncomponents thereof, then, by means of a suitable sequence of rotationalmovements of the drone, the desired magnetic profile can nevertheless besubstantially reproduced.

FIG. 7 finally shows a schematic illustration of a mine-sweeping system21 according to a further example of the invention. The mine-sweepingsystem illustrated here has a guiding drone 22 which can be constructed,for example, similarly to the drone 22 of FIG. 2. In particular, saidguiding drone 22 can be a self-driven drone and can carry out similartranslational movements and rotational movements as the drone of FIG. 2.In addition, the mine-sweeping system 21 of FIG. 7 also has two furtherdrones 71 which are connected to the guiding drone 22 by a towing cable72. This multi-sectional mine-sweeping system is also configured overallfor forming a predefined magnetic profile at a target location 26. Forthis purpose, each of the drones 22 and 71 has at least one magnetelement. The two rear drones 71 are also designed to in each case carryout rotational movements independently of one another with respect to atleast one degree of rotational freedom. By means of this plurality ofrotatably designed drones 22 and 71, the desired magnetic profile can bemodulated even more accurately in detail at the target location 26. Theoutlay on apparatus (i.e. in particular the number of drones and/or thespatial extent of the chain) can advantageously be kept smaller herethan in the prior art because of the use of the rotational movements.

LIST OF REFERENCE SIGNS

-   1 Magnetic signature-   20 Water-   21 Mine-sweeping system-   22 Drone-   23 Electric motor-   24 Propeller-   25 Control element-   26 Target location-   27 a Coil element-   27 b Coil element-   28 Permanent magnet-   29 Water surface-   31 Rectangular coil-   61 Magnitude of the magnetic flux density-   62 Magnetic flux density-   63 Revolution angle in degrees-   71 Drone-   72 Towing cable-   A Longitudinal axis-   B Magnetic flux density-   Br Radial component of the magnetic flux density-   Bt Tangential component of the magnetic flux density-   Bx Profile of the flux density along the x axis-   By Profile of the flux density along the y axis-   Bw Profile of the flux density along the direction w-   d Distance from the center of gravity-   M Center point of the coil element-   P Pole axis-   P1 First pole axis-   P2 Second pole axis-   r1 First degree of rotational freedom-   r2 Second degree of rotational freedom-   r3 Third degree of rotational freedom-   T Diving depth-   v Direction of travel-   w Diagonal direction in space in yz plane-   x,y,z Cartesian directions in space

1.-15. (canceled)
 16. A method for operating a mine-sweeping system,wherein the mine-sweeping system comprises at least one drone fordetonating sea mines, wherein the drone comprises at least one magnetelement for magnetically detonating the sea mines, wherein the methodcomprises: a) translationally moving the at least one drone in thewater, and b) carrying out a first rotational movement of the drone withrespect to a first degree of rotational freedom, characterized in thatthe drone has a longitudinal axis, wherein the first degree ofrotational freedom corresponds to a rotational movement about thelongitudinal axis.
 17. The method as claimed in claim 16, furthercomprising: c) carrying out a rotational movement of the drone withrespect to an additional second degree of rotational freedom.
 18. Themethod as claimed in claim 17, further comprising: d) varying a divingdepth of the drone.
 19. The method as claimed in claim 16, wherein theat least one magnet element of the drone is a permanent magnet.
 20. Themethod as claimed in claim 16, wherein the at least one magnet elementof the drone is an electrical coil element.
 21. The method as claimed inclaim 20, further comprising: e) varying an operating current of theelectrical coil element over time.
 22. The method as claimed in claim16, wherein the drone is a self-driven drone.
 23. The method as claimedin claim 16, wherein steps a) and b) take place simultaneously.
 24. Themethod as claimed in claim 16, wherein steps a) and b) take placesuccessively.
 25. The method as claimed in claim 16, wherein themine-sweeping system comprises a plurality of drones for detonating seamines.
 26. A mine-sweeping system, comprising: at least one drone fordetonating sea mines, wherein the drone comprises at least one magnetelement for magnetically detonating the sea mines, wherein the dronecomprises at least one control element for bringing about a firstrotational movement of the drone with respect to a first degree ofrotational freedom, wherein the drone has a longitudinal axis, whereinthe first degree of rotational freedom corresponds to a rotationalmovement about the longitudinal axis.
 27. The mine-sweeping system asclaimed in claim 26, wherein the at least one drone is a self-drivendrone.
 28. The mine-sweeping system as claimed in claim 26, wherein thecontrol element is a rudder, a flap, or a motor.
 29. The mine-sweepingsystem as claimed in claim 26, wherein the mine-sweeping systemcomprises a plurality of drones for detonating sea mines.